1. Field of the Invention
The present invention relates generally to a support structure for heat dissipation unit, which can substitute for the sintered powder body to greatly enhance the vapor-liquid circulation efficiency of the working fluid.
2. Description of the Related Art
Along with the rapid advance of scientific and technologic industries, electronic devices have more and more powerful functions. For example, the operation speed of central processing unit (CPU), chip set and electronic components of display unit has become faster and faster. This leads to higher heat generated by the electronic components per unit time. In case that the heat is not dissipated in time, the operation of the entire electronic device will be affected or even the electronic components will burn out.
In general, the heat generated by the electronic components is dissipated by means of cooling fan, heat sink or heat pipe. The heat sink is in contact with a heat source. Via the heat pipe, the heat generated by the heat source is transferred to a remote end for dissipating the heat. Alternatively, the cooling fan can forcedly guide airflow to carry away the heat of the heat sink. With respect to a narrow space or a large-area heat source, a vapor chamber is often selectively used as a heat conduction member for dissipating the heat.
A conventional vapor chamber is composed of two board materials mated with each other. The board materials are mated with each other to define a closed chamber in a vacuum state. The closed chamber has support structure and capillary structure. The support structure is generally classified into two types. The first type of support structure has capillary structure on outer side, which is formed of sintered powder.
Accordingly, the support structure not only can provide support effect, but also can make the working fluid flow from the condensation end of the upper board back to the evaporation end of the lower board under capillary attraction so as to achieve vapor-liquid circulation effect. The second type of support structure is entirely formed of sintered copper powder. Similarly, the second type of support structure not only can provide support effect, but also can make the working fluid flow from the condensation end of the upper board back to the evaporation end of the lower board.
However, there is a problem existing in the conventional vapor chamber, that is, the denser the porosity of the capillary structure (the sintered powder body) of the support structure is, the greater the capillary attraction of the capillary structure is. While the capillary attraction of the capillary structure is increased, the resistance against the fluid is increased. The capillary attraction of the capillary structure of the sintered copper powder and the resistance against the fluid are two factors conflicting with each other. As a result, even under the capillary attraction of the capillary structure (the sintered powder body) of the support structure, the condensed working fluid can hardly quickly flow back to the evaporation end of the lower board. Therefore, the flowability of the vapor-liquid working fluid is poor and the heat dissipation efficiency is lowered.
According to the above, the conventional vapor chamber has the following shortcomings:    1. The flowability of the vapor-liquid working fluid is poor.    2. The heat dissipation efficiency is lowered.